Metal detection systems have been used for more than thirty years, and have been capable of determining the presence or absence of a metallic object. Such systems have found many applications in various fields, and more recently, such systems have been finding widespread use as weapons detector devices. However, these systems when used for weapons detection have not been able to readily distinguish between various types of metallic objects.
These systems use an induction coil to which an oscillating signal is applied. Detection readings heretofore have been limited to a general determination as to the presence of a metal object with no precision in the identification process.
It has now been discovered that information can be developed which will permit this type of detection system to make specific identification of objects having conductive properties, and to give repeatable data for a specific object.
Previous systems have limited application because of their inability to distinguish between different types of objects, and in the use of these systems for detection at airports, there has been a persistent false alarm problem.
With the development of the system of this invention, it is now possible to accurately obtain information with respect to the type of conductive object disposed in the coil field, including information as to the various metallic components that are contained in it if there is more than one metal. This makes it possible to readily screen for different types of metallic objects of interest to preclude false alarms.
In addition, the system of this invention represents a break-through in that accurate repetitive readings can be obtained which make it possible to apply such systems to other areas, such as metal classification, sampling, testing of conductive solutions, animal tissues, and for tagging techniques.